org.apache.crunch.io.avro.AvroFileReaderFactory.java Source code

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Here is the source code for org.apache.crunch.io.avro.AvroFileReaderFactory.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.crunch.io.avro;

import java.io.IOException;
import java.util.Iterator;

import org.apache.avro.Schema;
import org.apache.avro.file.DataFileReader;
import org.apache.avro.generic.GenericDatumReader;
import org.apache.avro.io.DatumReader;
import org.apache.avro.mapred.FsInput;
import org.apache.avro.reflect.ReflectDatumReader;
import org.apache.avro.specific.SpecificData;
import org.apache.avro.specific.SpecificDatumReader;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.crunch.MapFn;
import org.apache.crunch.fn.IdentityFn;
import org.apache.crunch.io.FileReaderFactory;
import org.apache.crunch.io.impl.AutoClosingIterator;
import org.apache.crunch.types.avro.AvroType;
import org.apache.crunch.types.avro.Avros;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

import com.google.common.collect.Iterators;
import com.google.common.collect.UnmodifiableIterator;

public class AvroFileReaderFactory<T> implements FileReaderFactory<T> {

    private static final Log LOG = LogFactory.getLog(AvroFileReaderFactory.class);

    private final DatumReader<T> recordReader;
    private final MapFn<T, T> mapFn;

    public AvroFileReaderFactory(AvroType<T> atype) {
        this(createDatumReader(atype), atype);
    }

    public AvroFileReaderFactory(DatumReader<T> reader, AvroType<T> atype) {
        this.recordReader = reader != null ? reader : createDatumReader(atype);
        this.mapFn = (MapFn<T, T>) atype.getInputMapFn();
    }

    public AvroFileReaderFactory(Schema schema) {
        this.recordReader = new GenericDatumReader<T>(schema);
        this.mapFn = IdentityFn.<T>getInstance();
    }

    static <T> DatumReader<T> createDatumReader(AvroType<T> avroType) {
        if (avroType.hasReflect()) {
            if (avroType.hasSpecific()) {
                Avros.checkCombiningSpecificAndReflectionSchemas();
            }
            return new ReflectDatumReader<T>(avroType.getSchema());
        } else if (avroType.hasSpecific()) {
            // Use the classloader of the avro type as the classloader
            // for loading SpecificData classes. This is a best-effort
            // approach to avoid running into AVRO-1240. We can't just
            // use the SpecificDatumReader(Class) constructor because the
            // type class here isn't necessarily a SpecificData class, it
            // might just contain one as a subtype.
            return new SpecificDatumReader<T>(avroType.getSchema(), avroType.getSchema(),
                    new SpecificData(avroType.getClass().getClassLoader()));
        } else {
            return new GenericDatumReader<T>(avroType.getSchema());
        }
    }

    @Override
    public Iterator<T> read(FileSystem fs, final Path path) {
        this.mapFn.initialize();
        try {
            FsInput fsi = new FsInput(path, fs.getConf());
            final DataFileReader<T> reader = new DataFileReader<T>(fsi, recordReader);
            return new AutoClosingIterator<T>(reader, new UnmodifiableIterator<T>() {
                @Override
                public boolean hasNext() {
                    return reader.hasNext();
                }

                @Override
                public T next() {
                    return mapFn.map(reader.next());
                }
            });
        } catch (IOException e) {
            LOG.info("Could not read avro file at path: " + path, e);
            return Iterators.emptyIterator();
        }
    }
}